1. Field of the Invention
The present invention relates to a wafer exposure apparatus used in a semiconductor device manufacturing process, and more particularly, to an exposure apparatus capable of continuously exposing front and rear surfaces, or a specific surface, in a state that a wafer is aligned to the exposure apparatus.
2. Discussion of Related Art
Generally, in order to form a predetermined pattern on a wafer (sample) in a semiconductor device manufacturing process, after forming a predetermined layer, the predetermined layer is patterned through photolithography and etching processes. At this time, the photolithography process includes exposure and development processes for forming a pattern using a photosensitive layer.
The exposure process is a process of exposing the photosensitive layer using a predetermined mask, after mounting the wafer having the photosensitive layer on an exposure apparatus, which is classified into a contact alignment method of exposing the wafer and the mask in direct contact with each other, a proximity alignment method of exposing the mask and the wafer spaced apart from each other, and a stepper alignment method of repeatedly exposing a fine pattern or a precise pattern, depending on the type of the exposure apparatus.
FIG. 1 is a schematic view of a conventional exposure apparatus using a proximity alignment method, and light provided form a light source 1 is reflected by a reflective mirror 2 to be collected to a mirror 3. The light reflected by the mirror 3 progresses through an optical system formed of a plurality of lenses, re-reflected by a mirror 5, and then irradiated to a wafer 8 fixed to a holder or a chuck 9 through a lens 6. At this time, the light selectively passes through a mask 7 disposed on the wafer 8 and having a pattern to exposure only a desired portion of the photosensitive layer.
The conventional exposure apparatus is configured to expose only one surface of the wafer in a state that the wafer is approximately horizontally aligned, and in the case of exposing the other surface of the wafer, the wafer should be re-mounted. Therefore, since the wafer should be detached in order to exposure the other surface of the wafer, it may be troublesome to perform the increased number of processes, and a rear surface of the wafer may be damaged (marked) due to scratch of the wafer in contact with the chuck while the wafer is attached or detached. In particular, the processed wafer has a step to make it difficult to mount the wafer on the chuck, the processed surface of the wafer may be damaged, and an alignment error may also be generated.